Font rendering

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Original author	Amir Hassan (kallaballa) amir@.nosp@m.viel.nosp@m.-zu.o.nosp@m.rg
Compatibility	OpenCV >= 4.7

Render Hello World

Draws "Hello World" to the screen using NanoVG. Demos some basic font options.

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#include <opencv2/v4d/v4d.hpp>
 
using namespace cv;
using namespace cv::v4d;
 
class FontRenderingPlan: public Plan {
    //The text to render
    string hw_ = "Hello World";
public:
    void infer(Ptr<V4D> win) override {
        //Render the text at the center of the screen. Note that you can load you own fonts.
        win->nvg([](const Size &sz, const string &str) {
            using namespace cv::v4d::nvg;
            clear();
            fontSize(40.0f);
            fontFace("sans-bold");
            fillColor(Scalar(255, 0, 0, 255));
            textAlign(NVG_ALIGN_CENTER | NVG_ALIGN_TOP);
            text(sz.width / 2.0, sz.height / 2.0, str.c_str(),
                    str.c_str() + str.size());
        }, win->fbSize(), hw_);
    }
};
 
int main() {
    cv::Ptr<V4D> window = V4D::make(960, 960, "Font Rendering");
    window->run<FontRenderingPlan>(0);
}